Patent GB-704639-A (GB)
Title: Tension lock-up for printing plates
IPC: B41F27/10
Filed: 1951-10-11
Abstract: 704,639. Printing-plate clamps. GOSS PRINTING PRESS CO. Oct. 11, 1951 [March 31, 1951], No. 23715/51. Class 100 (2) A clamping device engaging pockets 25, 26, Fig. 3, formed at the ends of a printing plate 21 so as to hold it on a cylinder 18 comprises a fingerbar 40 having pocket-engaging fingers 41 extending upwardly therefrom, means for moving the finger bar through a limited range of adjustment to engage and disengage the fingers from the pockets and means causing retraction of the fingers below the surface of the cylinder when moved beyond the fully withdrawn position. Longitudinal flat bottomed slots 36 formed in the cylinder house the clamping mechanism and are closed by cover plates 60 apertured at 62 to pass the fingers 41. Each finger bar 40 is supported on a cam bar 45 resting on the bottom of the slot 36. Springs 73, Figs. 6, 7 and 10, attached to the ends of the finger bar and cam bar urge them together, towards the position shown in Fig. 3, in which the faces 71, 72 are in abutment. The cam bar 45 is movable broadwise by means described below and has somewhat rounded ends 45a to allow some tilting about its longitudinal centre to compensate for a slight skewness in the positioning of the plate on the cylinder. Movement to the right of cam bar 45 in Fig. 3 causes similar movement of the finger bar by abutment between faces 71, 72 and engages the fingers in the pockets 25. Movement to the left first disengages the fingers from the pocket and then by abutment with the sloping faces 62a of apertures 62 causes retraction of the fingers as shown in Fig. 6. Inclined surfaces 76, 77 on the finger bar coact with similar surfaces 78, 79 on the cam bar to allow movement of these bars radially towards each other. Retraction of the fingers 41 allows them to be overlaid by a printing plate of a larger size attached to the cylinder. The fingers 41, at the leading edge of the printing plate, are used to position the plate while other fingers 51 at the trailing end of the plate are used to clamp the plate to the cylinder. Adjustment of the position of the fingers 41 is effected as shown in Figs. 7, 8. The cam bar 45 is formed with an inclined cam slot 90, Fig. 7, in which slides a cam 91 mounted on a cam block 92, Fig. 8, by means of a pin 93. Longitudinal displacement of the cam block 92 by means of a screwed rod 94 actuated by a wrench-receiving head 95 will therefore cause broadwise movement of the cam bar 45 and finger bar 40. The cam bar 55 controlling the finger bar 50 carrying the trailing end clamping fingers 51 is similarly displaced by cams 128, 129, Fig. 7, engaged in a pair of oppositely inclined slots 126, 127 and urged apart to apply clamping pressure by a spring 135, Fig. 8, mounted on a rod 136. The rod 136 is threadably engaged with nuts 139, 139a and by rotation may cause the nuts to bear on the blocks 131, 132 carrying the cams 128, 129 and so cause sideways displacement of the cam bar 55 and finger bar 50 and disengagement and retraction of the fingers. By this means the clamping pressure is predetermined by the strength of spring 135 and the plate cannot be overstressed. To adjust the position of the plates axially of the cylinder recesses 21a, Fig. 10, are formed in the sides of the plate 21 at the leading end to receive projections 41a formed on the fingers 41 so that endwise movement of the finger bar will cause similar movement of the printing plate. Blocks 100, slidably mounted in slots 37 below slots 36 are displaceable over a short distance by a screwed rod 103 rotated by a wrench receiving head 105. A pin 101 extends upwardly from the block 100 through an opening 101a in the cam bar 45 to engage in a recess 102 in the finger bar. By rotation of the head 105 therefore, the leading end of the printing plate can be correctly positioned. A similar adjustment means is provided at the trailing end of the plate comprising a sliding block 110, Fig. 8, controlled by a screwed rod 113. The adjusting and tensioning mechanism can be removed as a unit from the slots 36 by first removing cover-plates 60 and a locating plate 153, Fig. 10, which engages a cutaway 154 in an insert 141, providing bearings for the control rods 94, 103. The insert can then be slidden out of the bore 142 in the bearing ring 38 and the whole assembly lifted radially out of the slot 36. The finger bar and cam bar may be keyed together to ensure correct relative movement by a key located in slots inclined so as to be parallel to the surfaces 78, 79. In a modification the finger bar and cam bar are connected, as shown in Fig. 15, by a rod 172 engaged in V slots 170, 171. The front sides of the bars are urged apart by a spring 173. In this form retraction of the fingers by engagement with the surface 62a is caused by a pivoting movement about rod 172 and compression of spring 173. Engaging and disengaging movements are, as before, linear. A plate cylinder may be arranged to hold a member, e.g. four, plates side by side in which case controlling units, e.g. as shown in Fig. 14a, are provided at each end of each groove, the blocks 100 providing axial adjustment for two plates and blocks 92 providing circumferential adjustment of the same two plates. Specifications 622,473 and 702,459 are referred to.